Many people think with either their wallets or their stomachs. Taking advantage of that can be used to reduce greenhouse gas emissions.

A tax on meat and milk would likely mean we'd buy less of the foods that contribute to climate change. And that's good for the environment, said a study published in the journal Climate Change.

"This tax is not at all a matter of forcing people to become vegetarians but merely moving toward a slightly more climate-smart diet," said one of the study's authors, Stefan Wirsenius of the University of Gothenburg, Sweden, in a press release.

Tacking about $82 onto the cost of beef for every “ton of carbon dioxide equivalent” would reduce Europe's beef consumption by 15 percent. By taxing all meats and milk, Europe's greenhouse gas emissions would be reduced by about 7 percent, according to the study.

“A ton of carbon dioxide equivalent” is the amount of a greenhouse gas needed to equal the heat-trapping power of one ton of carbon dioxide.

The greenhouse gas produced by cattle is methane, a gas 20 times more effective than carbon dioxide at trapping heat. Cows produce methane in their stomachs. The gas then exits the cow through both ends, mostly as belches, but some as flatulence.

Many cattle are fed on corn and other fodder fertilized with nitrogen. Some of that fertilizer is broken down by soil bacteria and turned into nitrous oxide, another greenhouse gas. Discovery News recently reported on farming methods that can reduce the amount of nitrous oxide produced.

"Today we have taxes on petrol and a trading scheme for industrial plants and power generation, but no policy instruments at all for food-related greenhouse gas emissions. This means that we do not pay for the climate costs of our food," another author of the study, Fredrik Hedenus of Chalmers University, said in the press release.

The problem with controlling greenhouse gas emissions from agriculture is that they are very difficult to monitor and measure.

"A tax on the emissions from food production would normally be preferable. But as this is virtually impossible in practice, and the effects of switching away from meat and milk are so great, we show that it can be far more effective to apply the tax directly to the meat and milk consumption," said Wirsenius.

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The study proposes taxing pork less than beef, and chicken less than both. This makes sense because beef requires the most food and water to produce and the cows themselves release more gas than the other animals.

The study proposes taxing pork less than beef, and chicken less than both. This makes because since beef requires the most food and water to produce and the cows themselves release more gas than the other animals.

The benefit of a tax is that it doesn't require new technologies and could be implemented as soon as legislation was passed. Economically encouraging people to change their eating habits would not only be good for the environment, but would free up land for other uses.

Far more food can be produced on land farmed for beans, corn and other crops, than if it was used for cattle pasture or producing animal feed. That food could be used to fill the bellies of the millions of hungry people on the planet.

Or the land could be used to grow biofuels. The reduction in greenhouse gases could be 15 times greater if the land freed up was used to grow biofuels, according to the study.

"If the world decides on substantial reductions in global greenhouse gas emissions, land will become a scarce resource, as a lot of land may be needed for bioenergy. Land-efficient food production and consumption will therefore become increasingly important. And beef production requires 20 times more land per kcal than beans," said Hedenus.